goprotobuf: ignore overridden package names for import name selection.
goprotobuf: ignore overridden package names for import name selection.

R=r
CC=golang-dev
http://codereview.appspot.com/4272048

andrewzeneski/goprotobuf,polydawn-ports/goprotobuf,wfxiang08/goprotobuf,go-mirrors/goprotobuf,liumuqi/goprotobuf,adwinsky/goprotobuf,ruiaylin/goprotobuf,t3rm1n4l/goprotobuf,tonnerre/go-protobuf,supiyun/goprotobuf,VividCortex/goprotobuf